1. Field of the Invention
The present invention relates to a robot hand and a robot.
2. Description of the Related Art
A method for manipulating a robot hand with a plurality of fingers to stably grasp an object for a required work has been studied. A fingertip tactile sensor device is required for such grasping to detect a contact force and a contact condition between the respective finger-tips and the object.
The conventional fingertip tactile sensor devices of this type have been developed and experimentally made as a touch sensor, most of which have such a complicated structure that numerous tactile elements are arranged in a matrix on a fingertip of a robot hand. Such fingertip tactile sensor devices fail to conduct accurate measurement in an area between the tactile elements, thus necessitating numerous tactile elements with high density on a fingertip of a robot hand.
However, if numerous tactile elements are disposed on a fingertip of a robot hand, it would be difficult to make the robot hand compact, and arrangement of signal lines for pressure detection would be extremely complicated. Also the fingertip could not be formed in a desired shape.
Further, it is normal to drive each of the finger joints of the robot hand through a wire by a motor distant from the joint without an actuator therein, requiring a long wire and complicated wiring. The contact force could be measured from a tension on the wire at the motor in such arrangement. However, the drive wire for the foremost joint tends to have a frictional force acting thereon along the wiring, so that the measurement of contact force may not be accurate through determining the tension of the wire at the motor.
For solving the above problems, a fingertip tactile sensor has been developed, in which a cavity provided in a fingertip cap is connected through a tube to a pressure detector for detecting a pressure change in the cavity due to a force applied onto the outer face of the cap. The pressure detector is located at a position where it will not interfere with the motion of the robot hand. This arrangement, however, requires a tedious setting of a tube upon attachment or exchange of fingertip tactile sensor. Furthermore, since the pressure detector is distant from the fingertip cap by the length of the tube, the response is slow to detect the contact force. In addition, when an object contacts the fingertip near the edge of the cavity, an output decreases from the pressure detector. The output from the pressure detector is affected by a difference in contact position on the outer face. Then, in the case where the contact position significantly changes on the outer face of fingertip upon manipulation of the object with fingertip, the contact force may not be accurately detected, presenting another problem.